I. Field of the Invention
The present invention is directed to machining tools and more particularly to an improvement in monotonic broach cutters.
II. Description of the Prior Art
Monotonic broach-type cutters employ tool inserts carried on a rotatable disk for performing machining operations on a workpiece, for example, for facing or cheeking faces of counterweights on a crankshaft. The tool inserts can be carried on either or both of the outer circumfery of the disk and the face of the disk. In each case a chip gullet is provided in the disk adjacent to each individual tool insert in order to allow chips which are machined from the workpiece to be removed. The portion of the disk (including any set screw, retaining plate or other retaining means) which receives each tool insert, together with its associated gullet, defines a pocket.
Tools mounted in either fashion have a lead angle with respect to the workpiece of only a few degrees, usually equal to the side clearance angle, or "dish" angle. Because of further necessary negative clearance angles, these conventional tool inserts require an approximately 5-7 degree negative injury clearance angle.
While monotonic broach-type cutters function adequately for their intended purpose, their use has entailed some drawbacks. The cutting speed of these cutters has been extremely limited due to the required negative clearance angles and to limitations on the chip thickness which may be adequately removed. As a practical matter, when considered with the desired density for the tool inserts, space limitations severely inhibit the possible size of the chip gullets.
It should be noted that while cutters of these two types are disclosed in FIGS. 1-4, these specific cutters are not admitted to be prior art applicable against the present invention, especially in the disclosure of the radial stepping of the inserts, as taught by Applicant's own parent application. The specific cutters shown in FIGS. 1-4 are disclosed merely to exemplify certain known features of prior cutting disks used in both monotonic broach-type and other types of cutting and milling machines.